Isolation and Characterization of a Human Fibroblast Interferon Gene and Its Expression in Escherichia coli

Abstract

Human fibroblasts were induced for interferon synthesis, and the mRNA coding for interferon was partially purified. On this basis, double-stranded DNA copies were synthesized enzymatically and were inserted into cloning vehicles. A large collection of colonies containing chimeric plasmids was obtained. An RNA selection method was used for the identification of several individual clones containing the human fibroblast interferon (IFN-β) cDNA. From the nucleotide sequence of the cloned structural gene, the primary structure of the mRNA and, hence, of the protein itself was deduced. IFN-β is a polypeptide 166 amino acids long and contains a single site for N-glycosylation; IFM-β is normally made as a preinterferon containing a signal sequence that is 21 amino acids long. The interferon gene was inserted into an expression plasmid under thermoinducible control of the phage lambda P_L promoter. This allowed the synthesis of polypeptides in the bacteria, which for all physicochemical, biological, and immunologic properties tested closely resembled authentic IFN-β.